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Coal ignites opportunity for mechanical engineering undergraduates

Midway through their undergraduate careers at Lehigh, two mechanical engineering majors seized an opportunity to put aside textbooks and learn first-hand about the real world of coal-fired power plants.

Matt Cullen ’06 and William Bromby ’07 signed on as interns with Lehigh’s Energy Research Center and got an up-close look at boiler sootblowing, coal-drying and power-plant pollution control.

They gained an appreciation for the hundreds of variables that must be finely tuned for a power plant to achieve maximum energy efficiency while meeting environmental standards.

They learned the importance of clear, precise communication in negotiating with manufacturers of specialized equipment.

And they learned to value the teamwork required to find solutions when data is not 100-percent conclusive, as it can be with engineering problems.

Cullen served two internships with ERC. During the first, he spent three weeks analyzing data from two power-plant boilers that use intelligent sootblowing software developed by the ERC. Sootblowers use air or steam to remove deposits from boiler tubes.

If that temperature is allowed to increase too much, says Cullen, the result is a high rate of formation of slag deposits and an increase in nitric oxide (NOx) emissions, which are a cause of acid rain.

The sootblowers located downstream in the boiler must also be factored in, says Cullen, because they have a large effect on steam temperature and thus on a power plant’s thermal efficiency.

Thus, says Cullen, “To properly control the slag deposits and temperatures, you might need 30 groups of sootblowers in different regions of the boiler.”

Sootblowers and spreadsheets

During his first internship, Cullen analyzed spreadsheets of data generated by the sootblowers. These contained thousands of numbers, so many, he says, “that it took me 10 minutes just to scroll down to the bottom of the file. That was daunting, at first.”

Cullen’s task was to find the correlation between sootblowing and the various temperatures inside the boiler. This required him to analyze hundreds of variables that were constantly shifting.

“It’s hard to pinpoint the effects of all the sootblowers,” he says. “You look for general trends because the results are less than definitive. But real life is like that; sometimes you get inconclusive results.

“We were part of a project team so we had to record results and make recommendations in a way everyone could understand. Our findings were passed to the next person on the team who was responsible for determining the optimal boiler operating conditions. Everyone does a little piece, and everything comes together in an amazing project that otherwise could not be done.”

Cullen worked on the sootblower project with ERC research scientist Harun Bilirgen. “Dr. Bilirgen was a very good mentor,” he says. “I had to do a lot of learning on the job, and he was extremely patient. He gave me space to figure things out for myself but he also offered guidance to interpret results.”

In his internship, Bromby analyzed data taken from a power plant in Pennsylvania and one in Michigan. “The measurements pertained to the operation of catalytic reactors, which are used in boilers to control NOx emissions,” says Bromby.

Bromby’s task was to compare the benefits of different strategies for operating the catalytic reactors, known in the industry as Selective Catalytic Reduction (SCR) reactors.

“SCR reactors are massive, honeycombed structures that spray ammonia, which mixes with NOx to create water and elemental nitrogen, thus eliminating pollution,” says Bromby. “But you can also curb NOx by altering boiler settings.

“I had to analyze the data to try to detect trends relating to the amount of ammonia used and the optimizing of the selective catalytic reduction.

“I didn’t know much about power plants before,” says Bromby. “Now I feel like I know everything. I learned to use Microsoft Excel, and I got an insight into the importance of statistics. Plus, working with numbers really sharpened my analytical skills.”

Bromby worked with ERC associate director Carlos Romero. “I was going in circles for awhile,” he says, “but Dr. Romero pointed me in the right direction and guided me and extended my work.”

A second internship

Cullen did a second internship, this one for six weeks, in which he worked with Bilirgen and ERC associate director Nenad Sarunac to analyze the costs and benefits of drying lignite coal. The three designed a layout for the coal-drying system, which involved directing heat from a boiler to an inbed heat exchanger that blows hot air on the coal as a hair dryer would. The process makes it possible to increase the thermal efficiency of the power plant and to reduce pollutant emissions.

Lignite normally contains large quantifies of water. Cullen’s job was to obtain cost estimates for the equipment needed to remove moisture from the coal.

“This project turned out to be a reality check for me,” says Cullen. “I realized that nothing is as easy as you think it is going to be. Different heat exchangers have different thermal efficiencies. I had to find the optimal arrangement for the exchangers.”

Cullen used the Internet to locate and contact the manufacturers of heat-exchangers and fans.

“Most exchangers and fans are custom-made,” he says. “I gave manufacturers a set of numbers and they got back to me with specs and prices. We had to find the exact numbers to come up with the most accurate possible estimates of the cost. Sometimes a manufacturer didn’t make something that big. I spent a lot of time online, searching for, contacting and e-mailing manufacturing companies.

“The sootblowing project was the more predictable of my two projects. It was tricky, but you could come up with the answer if you just spent the time. Coal-drying was more challenging. You’re not only relying on yourself but on a lot of people who don’t have the same priorities as you do.”

After completing his bachelor’s degree, Cullen plans to stay at Lehigh to pursue a Ph.D. in mechanical engineering.

“Lehigh is the perfect balance between the educational and industrial environments. After working with the Energy Research Center, I feel better prepared to go to industry, if I decide that’s what I want.

“The faculty know how to get their ideas across. The research scientists are good at conveying ideas in ways you can understand. There are so many intricacies to power plants. The ERC scientists can filter the information so that it doesn’t overwhelm you at first. They don’t want to baby you but they also don’t want to bog you down.”

Lehigh’s Energy Research Center was founded in 1973 to seek solutions to the nation’s energy problems. The center, a multidisciplinary group of faculty, staff and students, conduct fundamental and applied research in energy conversion, power generation, environmental control, and other areas. ERC internships are available to undergraduate students during the summer, the winter holiday break and the regular academic year.